This invention relates to relates to motorcycle engines and, more particularly, to air cleaner base assemblies that couple an air cleaner to a carburetor or fuel injection system and provide conduits for venting blow-by gases from the crankcase into a venturi air intake thereof.
As internal combustion engines wear, the annular spaces between the pistons and the cylinder tend to increase. In the combustion chamber of each cylinder, an air-fuel mixture is ignited. The expanding gas mixture forces the piston upwards generating power from the engine. In the expansion process, part of the gas mixture is forced between the annular spaces between the piston and the cylinder into the crankcase. These xe2x80x9cblow-byxe2x80x9d gases, which also include oil mist and unburned fuel, accumulate in the crankcase and must be vented from the crankcase to the atmosphere to prevent a potentially dangerous pressure build-up in the crankcase.
Pollution control laws and regulations restrict the emissions from internal combustion engines. As exhaust gases from internal combustion engines have become cleaner, the blow-by gases have become a more significant fraction of the total pollution generated from internal combustion engines. In many localities, the pollution control laws and regulations are such that vapors from the crankcase of internal combustion engines must be cleaned prior to discharge into the atmosphere. One method of reducing the pollution associated with the blow by gases is to recycle the gases through the engine. In some four cycle, two cylinder engines manufactured by Harley-Davidson, crank case venting and cleaning is accomplished by a crankcase breather system that conducts blow-by gases from the crankcase to an air cleaner, from which the gases are recirculated back into the engine through the carburetor for burning in the engine cylinders. A crankcase breather system is also used for engines employing a fuel injection system.
By way of example, in the Harley-Davidson four cycle, two cylinder engines each cylinder includes a pair of push rods that extend from the crankcase into the cylinder head for operating the intake and exhaust valves. Each of the push rods is disposed within a hollow push rod tube that communicates with the crankcase (e.g. provide a passageway for blow-by gases in the crankcase). Upper ends of the push rod tubes communicate with a chamber in the middle rocker box of each cylinder head. On each downstroke of the piston in each cylinder, an umbrella valve attached to a center rocker spacer opens, permitting blow-by gases to pass into the middle chamber. From the middle chamber, the blow-by gases are conducted to a second, upper chamber in the rocker box, and thence, via passageways, through a pair of spaced-apart, threaded holes in a right side of the cylinder heads. The threaded holes in combination with hollow bolts enable a stock plastic backing plate to be secured to the cylinder heads. The hollow bolts provide a passageway for the blow-by gases to vent from the holes in the cylinder heads. In a stock version of the Harley Davidson engine with a carburetor, a stock plastic carburetor or backing plate is provided, together with a pair of rubber tubes to conduct the blow-by gases from the hollow bolts to an air cleaner element.
To improve and customize engine performance, many purchasers of Harley Davidson motorcycles owners remove and discard the stock carburetor backing plate, hollow bolts and rubber tubes and replace the system with a substitute crankcase breather system. These substitute crankcase breather systems, for instance, by improving air flow to the engine, can significantly improve the horse power of the engine within certain operational ranges. Examples of substitute crank case breather systems are described in U.S. Pat. No. 5,233,967 by Peller et al. and U.S. Pat. No. 5,937,816 by Wincewicz et al.
In the background Wincewicz et al., the disadvantages of the Peller system are described in detail, such as a large part count and vibration/seal problems. The large part count of the Peller system increases the installation, the manufacturing and the maintenance costs associated with utilizing the system. The vibration/seal problems, however, may cause oil leakage at the joint between the breather system and the cylinder head or air leakage where the system attaches to the carburetor. Such leakage problems are also characteristic of other types of breather systems, as well.
While the breather system of Wincewicz is suitable in most applications, one problem associated with this design is that the blow-by gases, which contain oil and fuel mist, are vented directly into the air cleaner. These blowby gases tend to foul the air cleaner which substantially increases the replacement frequency of the air cleaner. Both the Peller system and the stock Harley-Davidson breather system, incidentally, also suffer from this fouling problem. Another disadvantage of the Wincewicz system is that the blow-by gases are vented from the cylinder heads in a manner where they may interfere with one another. Since the blow-by gases are vented into a common communication channel, the portions vented during the piston downstroke in one cylinder, can interfere with outflow of blow-by gases from the other cylinder during its piston upstroke.
Accordingly, it would be desirable to provide a crank case breather system that is easy to install, utilizes a minimum number of components, eliminates airflow interference effects, preserves air cleaner performance and minimizes seal leakage problems.
This invention addresses the needs indicated above by providing a combination backing plate and crankcase breather for a motorcycle engine having at least a pair of cylinders, a cylinder head mounted on each cylinder and a valve for connecting each cylinder head to the crankcase for venting the crankcase through an exit port in the cylinder head. The combination includes two hollow bolt alignment members integrally connected by brackets to a support member. The support member includes a venturi air intake, an air cleaner support surface and a backing plate. The backing plate is adapted to allow the support member to be mounted to the air intake of the motorcycle engine. The air intake of the motor cycle engine may be connected to a carburetor or a fuel injection system. The air cleaner support surface is adapted to allow an air cleaner and air cleaner cover to be mounted to the combination. Each bracket includes a conduit that allows blow-by gases vented from the engine through exit ports in the cylinder heads to be conducted.to an exit port in the venturi air intake where the blow-by gases are mixed with outside air and recirculated into the engine.
One aspect of the present invention provides an air cleaner base assembly for a motorcycle engine including at least one cylinder head having a communication port for venting a crankcase, an air cleaner and an air intake port of a fuel system. The base assembly can be generally characterized as including: 1) an air cleaner support member having a first side positioned adjacent the air intake port and an opposite second side adapted to seat the air cleaner thereto, the support member further including a venturi portion defining an intake aperture extending from the second side to the first side, and having a transverse cross-sectional dimension substantially similar to that of the air intake port of the fuel system for air flow from the air filter, through the intake aperture and into the air intake port; and 2) a flange member mounted to the support member, and adapted to mount said support member to the cylinder head, the flange member defining a communication conduit extending therethrough, and having an entrance port in flow communication with the communication port of the cylinder head and an opposite exit port terminating at the venturi portion.
In particular embodiments, the flange member may further define a bolt alignment passage formed for coaxial alignment with the communication port of the cylinder head when mounted thereto. Thus, the base assembly may include a bolt member extending through the bolt alignment passage and the communication port to mount the air cleaner support member to the cylinder head. In addition, the communication conduit of the flange member may intersect the bolt alignment passage at the entrance port thereof and the bolt member may be configured to enable fluid communication between the communication port of the cylinder head and the entrance port of the communication conduit of the flange member. Further, the bolt member may include a flow passage extending through a shaft portion thereof to provide flow communication between the communication port and the entrance port where the flow passage of the bolt member may include a first opening terminating at a distal end of the shaft, and a second opening terminating at a side portion of the shaft proximate the communication conduit entrance port when the base assembly is mounted to the cylinder head. The longitudinal axis of the communication conduit may intersect the longitudinal axis of the bolt alignment passage at an angle of between about 30xc2x0 to about 60xc2x0.
In other embodiments, the flange member may include a bolt contact surface surrounding one end of the bolt alignment passage, and formed to forcibly engage a head portion of the bolt member during the mount and the base assembly may further include a first seal device cooperating with the head portion of the bolt and the contact surface to form a fluid tight seal there between during the mount. The first seal device may be provided by an O-ring disposed in an annular groove inset in the bolt contact surface and encircling the one end of the alignment bolt passage. Further, the flange member may include a cylinder head contact surface surrounding an opposite end of the bolt alignment passage, and formed to forcibly engage a sealing surface of the cylinder head during the mount. Therefore, the base assembly may include a second seal device cooperating with the cylinder head contact surface and the sealing surface of the cylinder head to form a fluid tight seal therebetween during the mount. In addition, the first seal device may be provided by an O-ring disposed in an annular groove inset in the bolt contact surface and encircling the one end of the alignment bolt passage, and the second seal device may be provided by an O-ring disposed in an annular groove inset in the cylinder head contact surface and encircling the opposite end of the alignment bolt passage
In yet other embodiments, a second flange member, spaced-apart from the first named flange member, mounted to the support member, and adapted to mount the second support member to a second cylinder head of the motorcycle, the second flange member defining a communication conduit extending therethrough, and having an entrance port in flow communication with a communication port of the second cylinder head for venting the crankcase, the communication conduit also including an opposite exit port terminating at the venturi. Each flange member may define a respective bolt alignment passage formed for coaxial alignment with the corresponding communication port of the corresponding cylinder head when mounted thereto. In additon, the base assembly may include a respective bolt member extending through the respective bolt alignment passage and respective communication port to mount the air cleaner support member to the respective cylinder head. In addition, each communication conduit of the respective flange member may intersect the respective bolt alignment passage at the respective entrance port thereof and each bolt member may be configured to enable fluid communication between the respective communication port of the respective cylinder head and the entrance port of the communication conduit of the respective flange member. The longitudinal axis of the respective communication conduit may intersect the longitudinal axis of the respective bolt alignment passage at an angle of between about 30xc2x0 to about 60xc2x0.
In another embodiment, each flange member may include a bolt contact surface surrounding one end of the respective bolt alignment passage, each bolt contact surface being formed to forcibly engage a head portion of the respective bolt member during the mount. Thus, the base assembly may further include a respective first seal device cooperating with the respective head portion of the corresponding bolt member and the respective contact surface to form a fluid tight seal therebetween during the mount. Further, each flange member may include a respective cylinder head contact surface surrounding an opposite end of the respective bolt alignment passage, each cylinder head contact surface being formed to forcibly engage a respective sealing surface of the respective cylinder head during the mount. Therefore, the base assembly may include a respective second seal device cooperating with the respective cylinder head contact surface and the respective sealing surface of the corresponding cylinder head to form a fluid tight seal therebetween during the mount.
Another aspect of the present invention provides a combination backing plate and crankcase breather assembly for a motorcycle engine having at least a first and a second cylinder, a cylinder head mounted on each cylinder, means for connecting the cylinder heads to the crankcase for venting the crankcase through an exit port on each cylinder head, an air intake port of a fuel system and an air cleaner. The assembly may be generally characterized as including: 1) a support member having a first side adapted to mount to the engine air intake, and an opposite second side adapted to seat the air cleaner thereto where support member may includes a venturi portion defining a centrally disposed intake aperture with a transverse cross-sectional shape substantially identical to a transverse-cross-sectional shape of the engine air intake, 2) securing structure configured to secure the air cleaner to the support member; 3) a pair of flange members each integrally connected to the support member and formed to mount the assembly to the cylinder heads, each integrally connected to one hollow bolt alignment member, each flange member defining a respective communication conduit extending therethrough, and each communication conduit having an entrance port in flow communication with a respective communication port of the corresponding cylinder head and an opposite exit port terminating at the venturi portion such that each communication conduit vents gases from the crankcase through the exit ports of the respective cylinder head to the corresponding exit port at the venturi portion; 4) a pair of hollow bolt members each adapted to releasably mount a respective flange member to the corresponding cylinder head, each bolt member including a flow passage coaxially aligned with the corresponding exit port of cylinder head when the bolt member is fastened in the respect exit port; and 5) respective sealing devices cooperating with at least one of the respective hollow bolt members and the respective flange members to fluid seal the respective communication conduit to the respective exit port.
These and other features of the present invention will be presented in more detail in the following detailed description of the invention and the associated figures.